In recent years, a type of mobile communications network known as an ad-hoc network has been developed. In this type of network, each mobile node is capable of operating as a base station or router for the other mobile nodes, thus eliminating the need for a fixed infrastructure of base stations. As can be appreciated by one skilled in the art, network nodes transmit and receive data packet communications in a multiplexed format, such as time-division multiple access (TDMA) format, code-division multiple access (CDMA) format, or frequency-division multiple access (FDMA) format.
More sophisticated ad-hoc networks are also being developed which, in addition to enabling mobile nodes to communicate with each other as in a conventional ad-hoc network, further enable the mobile nodes to access a fixed network and thus communicate with other mobile nodes, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet. Details of these advanced types of ad-hoc networks are described in U.S. patent application Ser. No. 09/897,790entitled “Ad Hoc Peer-to-Peer Mobile Radio Access System Interfaced to the PSTN and Cellular Networks”, filed on Jun. 29, 2001, now U.S. Pat. No. 7,072,650, in U.S. patent application Ser. No. 09/815,157entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel Data Channels with Separate Reservation Channel”, filed on Mar. 22, 2001, now U.S. Pat. No. 6,807,165, and in U.S. patent application Ser. No. 09/815,164 entitled “Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System”, filed on Mar. 22, 2001, now U.S. Pat. No. 6,873,839, the entire content of each being incorporated herein by reference.
Typically, to make routing decisions, routing algorithms need some criteria pertaining to the usability or quality of the potential links between nodes. Certain existing routing algorithms for routing packets between nodes in ad-hoc networks may ignore the behavior of wireless channels. For example, in first generation wireless routing algorithms, the criteria is typically the existence of a link between nodes. In these algorithms, therefore, routing is based on optimizing the number of hops for the route. The optimal route is identified thus to be the route having the lowest total number of hops.
In second generation wireless routing algorithms, additional information is gathered, such as the reliability, bandwidth, signal strength and other such parameters, as can be appreciated by one skilled in the art. The routing algorithms use this information in a raw or filtered format to select the links that should be used for communication between nodes. Also, a simple prediction of the future parameters of the links can be performed using a linear prediction algorithm as can be appreciated by one skilled in the art. Although these algorithms may be somewhat suitable, they may not respond to quick changes in channel properties. For example, when Rayleigh fading occurs on a mobile channel because a wireless node travels into an area having many obstructions, the algorithm may not account for the fact that such fading can occur rapidly. Also, selecting a link based on a prediction algorithm before the transmission occurs may be unsuitable for transmissions that are broadcast in nature and are received by multiple destinations or intermediate nodes, since some of those nodes may be in an environment prone to fading when the transmission actually occurs.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.